Transient Voltage Surge Suppression (TVSS) devices use Metal Oxide Varistors (MOVs). A MOV is connected between an A.C. power line and a neutral line. The MOV becomes conductive during a voltage transient. In the conductive state, the MOV temporarily discharges the voltage transient to the power line. When MOVs fail they can create a short circuit that draws excessive A.C. current from the power line. This excessive current is drawn though the MOV circuit until the fuse in the electrical circuit clears or until a circuit breaker opens. Until the fuse or circuit breaker opens, a large current is conducted through the circuit possibly causing catastrophic results such as extensive smoke, mechanical damage and fire.
A small fuse could be used in the surge suppression system to limit the over current condition and prevent this type of damage. However smaller fuses severely limit the ability of the MOV to temporarily short transient voltage surges.
Multiple MOVs are often connected together in parallel to share transient voltage spikes. The multiple MOVs are typically located in the same enclosure. If a voltage spike or power surge is in excess of the combined energy handling capability of the multiple MOVs, one or more of the fused MOVs blow. Other MOVs and electrical equipment in the enclosure may be damaged by an explosion or fire that happens during the power surge condition. This may prevent some or all of the MOVs in the enclosure from providing protection during subsequent power surges. Further, the MOVs are typically contained inside a plastic enclosure. If the explosion is severe enough, the smoke and explosion from the power surge event may destroy the plastic enclosure and other electrical equipment located next to the enclosure. For example, the electrical surge event may damage electrical equipment in a load center or transfer switch containing the surge suppressor, resulting in large monetary losses.
The present invention addresses this and other problems associated with the prior art.